JP2002186172A - Inverter power generator and control method in overloaded condition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method in an overloaded condition of an inverter power generator, which enables the drive of an induction motor requesting a large drive current and realizes an adequate protection in the overload condition. SOLUTION: When the load current of the inverter, detected with a load current detector 12, is within the range of a first overload discriminating value or higher and a second overload discriminating value or less, and if an overload continuation time exceeds a first setting time, the supply of a drive signal to a switching circuit 5 is stopped to stop the operation of the inverter. If a load current exceeds a second overload discriminating value and the output voltage of the inverter is higher than a short-circuit discriminating value, and when the overload continuation time exceeds a second setting time preset depending on an output voltage of the inverter, operation of the inverter is stopped, and if the load current exceeds the second overload discriminating value and the output voltage of inverter is equal to the short-circuit discriminating value or smaller, the operation of the inverter is stopped immediately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter having an AC generator driven by an internal combustion engine at various rotational speeds, and an inverter for converting the output of the AC generator into an AC output having an arbitrary frequency. The present invention relates to a power generator and a control method at the time of overload.

[0002]

2. Description of the Related Art An inverter power generator is used as a power generator using an internal combustion engine as a prime mover.

In general, an inverter generator includes an AC generator driven by an internal combustion engine, a DC power supply unit for converting an output voltage of the AC generator into a DC voltage, and an output voltage of the DC power supply unit having a predetermined frequency. An inverter that converts the voltage into an AC voltage.

The inverter includes a bridge-type switch circuit for converting the output of the DC power supply into an AC voltage by turning on and off a switch element, a filter circuit for removing a harmonic component from the AC voltage output from the switch circuit, A load connection terminal to which an output of the filter circuit is applied, and a PWM for performing PWM control on a switch element of the switch circuit so as to output an AC voltage having a desired waveform through the load connection terminal.
Control means.

The DC power supply unit includes a rectifier for rectifying the output of the AC generator and a smoothing capacitor connected between the DC output terminals of the rectifier, and generates a DC voltage across the smoothing capacitor. .

The bridge-type switch circuit comprises an upper switch element and a lower switch element connected in series with each other, and an upper feedback diode and an upper feedback diode connected antiparallel to the upper switch element and the lower switch element, respectively. It has a configuration in which a plurality of switch arms each including a feedback diode on the lower side are connected in parallel, and a pair of DC input terminals is derived from a common connection point on one end side and the other end side of the plurality of switch arms, An AC output terminal is derived from a connection point between the upper and lower switch elements of each of the plurality of switch arms.

The switch element of the above switch circuit is PWM.
The PWM control means for controlling, for example, sets at least one of the drive signals to be provided to a pair of switch elements at diagonal positions of the bridge of the switch circuit as a drive signal (PWM signal) having a PWM-modulated pulse waveform, and uses the PWM signal to perform the control. By turning on and off a current flowing through the switch element at a predetermined timing, an AC voltage having an intermittent waveform in which a duty value D changes every PWM cycle in accordance with an instantaneous value of an AC output voltage applied to a load through a load connection terminal is converted to an inverter. Output from the circuit.

A duty value D in the PWM control can be obtained by multiplying a reference duty value Do required for making a waveform of an AC output voltage output from a load connection terminal into a desired waveform by a correction coefficient Kv. Normal,
As the correction coefficient Kv, the ratio V between the rated value VA of the peak value of the AC output voltage obtained between the load connection terminals and the DC power supply voltage VD is used.
Use A / VD.

The intermittent waveform AC voltage output from the switch circuit is converted into a smooth waveform AC output voltage by removing its harmonic components by a filter circuit.

[0010] In addition, in order to protect the switch circuit and the like constituting the inverter from overcurrent, the inverter power generator is provided with overload protection means for stopping the operation of the inverter when the load current becomes excessive. The overload protection means provided in the conventional inverter power generator is:
A current transformer that detects a load current flowing from the inverter through the load connection terminal, and compares the load current detected by the current transformer with a limit value, and detects an overload when the detected load current exceeds the limit value. An overload signal generating circuit that generates a signal, and an inverter operation that stops the supply of a drive signal to a switch circuit of the inverter and stops the operation of the inverter when an overload signal is generated for a predetermined time. And stopping means.

When an inverter generator is used, a DC voltage output from a DC power supply unit can be converted into an AC voltage having an arbitrary frequency by controlling the inverter, so that it is not related to the rotation speed of the generator. Therefore, an AC voltage having a desired frequency can be obtained from the load connection terminal.
Further, by controlling the duty value that changes every PWM cycle in the PWM control, an AC voltage having an arbitrary magnitude can be obtained.

[0012]

As described above, in the conventional inverter generator, the operation of the inverter is stopped when the load current flowing from the inverter through the load connection terminal exceeds the limit value for a set time. The overload protection control is performed to protect the switching elements and the like constituting the switch circuit of the inverter from overcurrent. When driving an inductive load, the load may not be able to be started because the overload protection control may be activated by a large inrush current flowing at the time of starting and the operation of the inverter may be stopped.

In order to solve such a problem, it is conceivable that the limit value of the load current in the overload protection control is set higher than the rush current of the induction motor. When a load other than the inductive load is driven, the protection operation is not performed even if an overcurrent flows for a long time, so that the inverter cannot be properly protected.

An object of the present invention is to provide a method of controlling an inverter generator at an overload in which an inverter can be properly protected for both an inductive load and a load other than the inductive load. It is in.

Another object of the present invention is to provide an inverter generator capable of appropriately performing overload protection control for both inductive loads and loads other than inductive loads.

[0016]

SUMMARY OF THE INVENTION The present invention is an AC generator driven by an internal combustion engine, a rectifier for rectifying the output of the AC generator, and converting the output voltage of the rectifier into an AC voltage having a constant frequency. The present invention relates to a method for controlling an overload of an inverter power generator including an inverter for supplying a load to a load.

In the control method of the present invention, when it is detected that a load current exceeding the first overload judgment value set in the inverter flows, the measurement of the overload duration is started, and the load current is reduced to the first overload determination time. A determination as to whether or not a second overload determination value set larger than the overload determination value is exceeded;
It is determined whether the output voltage of the inverter is equal to or less than the short-circuit determination value, and immediately when the load current exceeds the second overload determination value and the output voltage of the inverter is equal to or less than the short-circuit determination value. Stop the operation of the inverter. When the load current is equal to or more than the first overload judgment value and equal to or less than the second overload judgment value, the operation of the inverter is stopped when the overload continuation time exceeds the first set time. When the current exceeds the second overload determination value and the output voltage of the inverter is higher than the short-circuit determination value, the overload duration time exceeds the second set time set in accordance with the output voltage of the inverter. Stop the operation of the inverter. Here, the second set time is set to be shorter as the output voltage of the inverter is lower.

The first overload determination value is a lower limit value of an overload current that is allowed to flow through the inverter during a first set time.

The second overload judgment value is an upper limit value of the overload current that can be supplied to the inverter during the first set time. The first and second overload determination values are appropriately set according to the current capacity of the switch element constituting the switch circuit of the inverter and the length of the first set time.

The first set time may be set to a fixed value, or may be changed according to the magnitude of the detected load current. That is, the first set time may be set according to the magnitude of the load current such that the larger the detected load current is, the shorter the first set time is.

The short-circuit judgment value is a judgment value for judging whether the output terminals of the power generator are short-circuited or in a state close to short-circuit. When the load connected between the terminals is in a transient state at the time of starting, the voltage is set to a value smaller than the minimum value of the voltage between both ends of the load.

For example, when the load of the inverter generator is an induction motor, the voltage across the induction motor when an inrush current flows when the induction motor is started (the voltage between the output terminals of the inverter generator). Is set to a value smaller than the lowest value of.

When the above-described control is performed, if the overload current is in the range of not less than the first overload judgment value and not more than the second overload judgment value, the overload continuation time is set to the first set time. Is exceeded, the operation of the inverter is stopped.

Therefore, by setting the first and second overload determination values to appropriate values, it is possible to perform the same overload protection control operation as that of the related art for loads other than the inductive load. Further, when the overload current exceeds the second overload determination value and the output voltage of the inverter becomes equal to or less than the short-circuit determination value, the operation of the inverter is immediately stopped, so that the output terminals of the inverter are short-circuited or short-circuited. When the state becomes close, the operation of the inverter can be immediately stopped to protect the inverter.

When the overload current exceeds the second overload judgment value and the output voltage of the inverter is higher than the short-circuit judgment value, the operation of the inverter is performed when the overload duration exceeds the second set time. Is stopped. Therefore,
By setting the second overload determination value and the short-circuit determination value to appropriate values, it is possible to drive an inductive load through which a large current flows at the time of startup without any trouble. For example, the second overload determination value is set higher than the peak value of the inrush current flowing when the induction motor starts, and the short circuit determination value is lower than the minimum value of the voltage across the induction motor when the inrush current flows. By setting, the induction motor can be started without any trouble.

An inverter generator for implementing the above method comprises an AC generator driven by an internal combustion engine, a rectifier for rectifying the output of the AC generator, and a converter for converting the output voltage of the rectifier into an AC voltage having a constant frequency. In the present invention, a load current detector that detects a load current flowing from the inverter to the load, and a load current that is detected by the load current detector are supplied to the first excess current. An overload signal generating means for generating an overload signal when the load value is equal to or more than an overload determination value; Overload current determining means for determining whether a load current exceeds a second overload determination value set to a value larger than the first overload determination value when a load signal is generated, and Short-circuit determining means for determining whether or not the output voltage of the inverter is equal to or less than a set short-circuit determining value when the load determining means determines that the load current exceeds the second overload determining value; By the short circuit judgment means,
A short-circuit inverter protection means for immediately stopping the operation of the inverter when it is determined that the output voltage of the inverter is equal to or less than the short-circuit determination value; and a magnitude of the load current determined by the overload current determination means. When the overload continuation time exceeds the first set time in a state where it is determined that the load current is equal to or less than the second overload determination value, and when the magnitude of the load current is equal to or smaller than the second overload determination value, When the overload continuation time exceeds the second set time in a state where it is determined that the overload determination value is exceeded and the output voltage of the inverter is determined to be higher than the short circuit determination value by the short circuit determination means. And overload inverter protection means for stopping the operation of the inverter. The second set time is set to be shorter as the output voltage of the inverter is lower.

In the above method, the output voltage of the inverter is compared with the short-circuit judgment value in order to judge whether or not the output of the inverter is short-circuited. It is also possible to determine whether the inverter is short-circuited or nearly short-circuited and the overload state from the size determination alone. That is, the value of the load current flowing through the inverter is compared with the allowable limit value and at least one overload determination value set to a value smaller than the allowable limit value, and when the load current exceeds the allowable limit value, Immediately stop the operation of the inverter, and when it is detected that the load current is below the allowable limit value and exceeds one of the overload judgment values, the time set according to the magnitude of the overload judgment value The operation of the inverter may be stopped when the time has elapsed.

In such a method, the inverter power generator compares the load current detected by the load current detector with the load current detector that detects the load current flowing through the inverter, and compares the load current with the allowable limit value. An instantaneous stop command generation circuit for generating a stop command for instructing to immediately stop the inverter when it is detected that the load current exceeds the allowable limit value, and a load current value detected by the load current detector. When it is detected that the value of the load current detected by comparing with the overload determination value set to a value smaller than the allowable limit value exceeds the overload determination value, the load current is determined according to the magnitude of the overload determination value. At least one overload stop command for performing a timed operation for a preset time and generating a stop command for instructing to stop the operation of the inverter when the timed operation is completed. It can be a circuit, a configuration in which any of the instantaneous stop command generating circuit or overload stop command generation circuit has an inverter stop means for stopping the operation of the inverter upon the occurrence of a stop command.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an inverter power generator 1 according to the present invention. In FIG. 1, reference numeral 2 denotes a three-phase magnet type AC generator, and reference numeral 3 denotes an internal combustion engine (E / G) that drives the AC generator 2. The AC generator 2 includes a multi-pole magnet rotor (not shown) and a stator having three-phase connected power generation coils 2u to 2w. The magnet rotor is an internal combustion engine. 3 is attached to the crankshaft.

Reference numeral 4A denotes a rectifier formed by connecting diodes Du to Dw and diodes Dx to Dz in a three-phase bridge. The three-phase AC input terminals 4u to 4w of the rectifier 4A are connected to the three-phase power generator 2 respectively. An output terminal is connected, and a smoothing capacitor Cd is connected between the DC output terminals 4a and 4b of the rectifier 4A. The rectifier 4A and the smoothing capacitor Cd constitute the DC power supply unit 4.

5 is a switch arm comprising a series circuit of an upper switching element Fu and a lower switching element Fx;
This is an H-bridge type switch circuit configured by connecting in parallel a switch arm composed of a series circuit of an upper switch element Fv and a lower switch element Fy.

In this example, each switch element is an IGBT
(Insulated gate type bipolar transistor), and each of the IGBs constituting the switch elements Fu and Fv
From the connection point between the emitter of T and the collectors of the IGBTs constituting the switching elements Fx and Fy, the AC output terminal 5
u, 5v are drawn out, and the DC input terminals 5a and 5b are drawn out from the common connection point of the collectors of the IGBTs constituting the switching elements Fu, Fv and the common connection point of the emitters of the IGBTs constituting the switching elements Fx, Fy, respectively. ing.

The switch circuit may be configured using another switch element that can be controlled on and off, such as a MOSFET or a bipolar power transistor.

The input terminals 5a and 5b of the switch circuit 5 are respectively connected to the output terminals 4a and 4b of the rectifier 4A, and the pair of output terminals 5u and 5v are of a low-pass type comprising inductances L1 and L2 and a capacitor C1, respectively. A pair of load connection terminals 7u and 7
v. A load 8 is connected between the load connection terminals 7u and 7v.

Reference numeral 10 denotes a power supply voltage detection circuit for detecting the DC power supply voltage output from the DC power supply unit 4, and 11 denotes a filter circuit 6.
Output voltage detection circuits for detecting the AC output voltage output from the amplifiers, each of which comprises an amplifier circuit constituted by operational amplifiers OP1 and OP2.

A load current detector 12 detects the load current of the inverter. In the example shown in the figure, the load current detector is attached to a line connecting the output terminal of the filter circuit 6 and the load connection terminal 7v. Current transformer CT. The load current detection signal Vi obtained from the load current detector 12 is input to the non-inverting input terminal of the comparator CP1, and is also input to the amplifier circuit 13 configured using the operational amplifier OP3. A first overload determination signal Vis1 obtained by dividing the output voltage of a DC constant voltage power supply circuit (not shown) by a voltage dividing circuit composed of a series circuit of resistors R1 and R2 is input to the inverting input terminal of the comparator CP1. ing.
The first overload determination signal Vis1 gives a first overload determination value is1 that defines the lower limit of the inverter overload range. When the load current of the inverter exceeds the first overload determination value, The output voltage of the comparator CP1 changes from a high level state to a low level state.

In the example shown in the figure, a first overload determination signal generation circuit is constituted by the resistors R1 and R2 and a DC constant voltage power supply circuit (not shown).
An overload detection circuit 14 (which detects that the inverter is in an overload state) generates an overload signal when the load current of the inverter becomes equal to or greater than the first overload determination value. Signal generating means). In this example, a decrease in the level of the output voltage of the comparator CP1 is used as an overload signal.

The outputs of the power supply voltage detection circuit 10, the output voltage detection circuit 11, the amplification circuit 13 and the overload detection circuit 14 are input to a controller 15 for controlling the switch circuit 5. The controller 15 includes an A / D converter 15a that converts an output of the power supply voltage detection circuit 10 into a digital signal and an A / D converter 15 that converts an output of the output voltage detection circuit 11 into a digital signal.
/ D converter 15b, an A / D converter 15c for converting a load current detection signal input through the amplifier circuit 13 into a digital signal, a CPU 15d,
A microcomputer having an OM and the like, and a CPU 15
d in response to the drive command signal output from switch d.
u, Fv, Fx, and Fy control terminals (IG in the illustrated example)
PWM signals Gu, Gv, Gx and Gy
And an output port 15e for providing

In the example shown in FIG. 1, the switch circuit 5 and
A filter circuit 6, a power supply voltage detection circuit 10, an output voltage detection circuit 11, a load current detector 12, an amplification circuit 13 for amplifying a load current detection signal, and an overload detection circuit 14.
And the controller 15 constitute an inverter that converts a DC voltage output from the DC power supply unit 4 into an AC voltage having a constant frequency. The inverter, the AC generator 2, and the DC power supply unit form the inverter power generator 1. It is configured.

In the inverter generator 1 shown in FIG. 1, the AC voltage output from the AC generator 2 is converted into a DC power supply voltage VD by a DC power supply unit 4 comprising a rectifier 4A and a smoothing capacitor Cd. The power supply voltage VD is input to the switch circuit 5 of the inverter.

The CPU 15d of the controller 15 stores the data AN of the DC power supply voltage VD supplied from the DC power supply section 4.
1 through the operational amplifier OP1 and the A / D converter 15a, and the load connection terminal 7 through the operational amplifier OP2 and the A / D converter 15b of the output voltage detection circuit 11.
The instantaneous data AN0 indicating the instantaneous value of the voltage between u and 7v is read. The CPU 15d calculates a duty value D of each PWM cycle based on these data, and sends the calculated duty value D to the control terminal of the switch element of the switch circuit 5 so as to interrupt the output of the switch circuit of each PWM cycle. Provides a PWM signal. Thereby, the load connection terminal 7
The switch circuit 5 outputs an AC voltage having an intermittent waveform whose duty value changes every PWM cycle according to the instantaneous value of the AC output voltage applied to the load 8 through u and 7v.

FIGS. 2A, 2B, 2C, and 2D show the case where a sine-wave AC output voltage is obtained between the load connection terminals, respectively.
It shows PWM signals Gu, Gy, Gx and Gv applied to control terminals of Fy, Fx and Fv. The switch elements Fu, Fy, Fx, and Fv are turned on when the PWM signals Gu, Gy, Gx, and Gv are at the H level, and are turned off when the PWM signals Gu, Gy, Gx, and Gv are at the L level. State.

FIGS. 2 (E) and 2 (F) show a pair of switch elements (Fu,
(Fy) and (Fx, Fv) show the timing at which they are simultaneously turned on. FIGS. 2G and 2H show two switch elements (Fu, Fv) constituting the upper side of the H-bridge, respectively.
v) shows the timing at which they are simultaneously turned on, and the timing at which the two switch elements (Fx, Fy) constituting the lower side are simultaneously turned on.

When the waveform of the AC output voltage output through the load connection terminals 7u and 7v is a sine waveform, a pair of switch elements Fu and Fy located at diagonal positions during a positive half-wave of the AC output voltage. By applying the PWM signals Gu and Gy having the pulse waveforms to the gates of FIG.
And a positive half-wave voltage of an intermittent waveform (a waveform similar to the waveform shown in FIG. 2E) in which the duty value changes every PWM cycle Δt in proportion to the instantaneous value of the sine wave AC voltage. From the switch circuit 5.

Also, during the period of the negative half-wave of the AC output voltage, by providing the PWM signals Gx and Gv having pulse waveforms to the gates of the pair of switch elements Fx and Fv at the diagonal positions, these switch elements are switched. An intermittent waveform (FIG. 2F) in which the ON period is simultaneously generated as shown in FIG. 2 (F), and the duty value changes every PWM cycle Δt in proportion to the instantaneous value of the sine wave AC voltage. ) Is output from the switch circuit 5.

The AC voltage having the intermittent waveform output from the switch circuit 5 is converted into a smooth sine-wave AC output voltage through the filter circuit 6, and then applied to the load 9 through the load connection terminals 7u and 7v.

The PWM signal is usually a pulse that alternates between a first state (H level in the example shown in FIG. 2) and a second state (L level in the example shown in FIG. 2). The switch element of the switch circuit 5 is turned on during a period in which the PWM signal is in the first state.
While the WM signal is in the second state, the switch element of the switch circuit 5 is turned off.

In the example shown in FIG. 2, the PWM signals Gu and Gx are pulse signals of opposite phases generated at a constant PWM period Δt, and the PWM signals Gy and Gv are P
By changing the duty value of each PWM signal for each PWM cycle Δt as pulse signals of opposite phases with a predetermined phase delay with respect to the WM signals Gu and Gx,
The switching circuit 5 outputs an AC voltage having an intermittent waveform whose duty value changes every PWM cycle Δt.

In the inverter power generating device shown in FIG. 1, as shown in FIGS. 2G and 2H, the period during which the switch elements Fu and Fv constituting the upper side of the bridge of the switch circuit are simultaneously in the ON state, and The switching pattern of the switch elements of the switch circuit is determined so as to generate a period in which the switch elements Fx and Fy constituting the lower side of the bridge are simultaneously turned on.

When the switching pattern is determined in this manner, the capacitor C1 of the filter circuit 6 is switched between the time when the upper switching elements Fu and Fv are simultaneously turned on and the time when the lower switching elements Fx and Fy are simultaneously turned on.
Of the load connection terminal 7
The AC output voltage obtained between u and 7v can be made a smoother waveform.

In this specification, in each PWM cycle Δt, a period during which the output voltage or the output current of the switch circuit is at a high level (a period during which the switch elements at diagonal positions of the switch circuit are simultaneously turned on) is a PWM cycle. The proportion occupied by Δt is defined as the duty value D of the PWM control.

When the controller 15 is constituted by using a microcomputer, each PWM cycle is detected by counting pulses generated at a constant cycle in the microcomputer by a PWM cycle counting counter, and each PWM cycle is detected. The start timing is referred to as switch timing.

The microcomputer 15d controls the switching elements Fu and Fx and Fv and Fy for P
An internal interrupt process is performed for each WM cycle Δt, and the on-time of the switch element is set in a PWM signal generation timer based on a duty value obtained by a method such as reading from a map in the internal interrupt process. While the measured ON time is being measured, the potential of the drive command signal output port of the CPU 15d is set to the first state (for example, H level state), and the drive command signals Gu, Gv, Gx having pulse waveforms are output from the output port 15e. And Gy.

FIG. 3 shows the internal interrupt timing (switch timing of the switch element of the switch circuit) when the waveform of the AC output voltage obtained between the load connection terminals is a sine waveform.
And shows the relationship between the duty value of the PWM signal and
In the figure, a is the waveform of the AC voltage obtained between the load connection terminals 7u and 7v, Δt is the PWM cycle, VA is the peak value of the AC voltage a, Vav is the average value of the AC voltage a, and T is the load connection terminal. This is the period of the AC voltage obtained in between.

In this case, the switch circuit 5 outputs an AC voltage having an intermittent waveform in which the duty value D changes every PWM cycle Δt according to the instantaneous value of the AC output voltage a obtained between the load connection terminals. The waveform of the AC voltage is a step-like waveform obtained by dividing one cycle of the sine wave AC voltage into n pieces. By passing this step-like AC voltage waveform through the filter circuit 6, harmonic components are removed and the load connection terminals 7u,
An output voltage having a smooth sine waveform is obtained between 7v.

When the output voltage of the inverter generator is an AC voltage having a sine waveform, the reference duty value Do of the output of the inverter is given by the following equation.

Do = Sin (2πnΔt / T) (1) where n is a numerical value indicating the number of the PWM cycle from the zero cross point at the rising edge of the AC voltage waveform, and counts the PWM cycle. Therefore, it is given by the count value of a counter provided in the controller.

In the PWM control performed by the controller 15,
Reference duty value Do given by the above equation (1)
Is multiplied by a predetermined correction coefficient Kv, which changes with the change of the DC power supply voltage VD, to obtain a duty value D.

The DC power supply voltage VD changes with respect to the output current ID, for example, as shown by a curve in FIG. Assuming that the maximum rated value of the peak value of the AC output voltage obtained between the load connection terminals 7u and 7v is VAmax, the operating point at that time is Pr Pr shown in FIG.
And the maximum rated load current is IDmax. Here, the maximum rated load current IDmax is the maximum load current allowed when obtaining an AC voltage having no waveform distortion between the load connection terminals. When a load current exceeding the maximum rated load current IDmax flows, the waveform of the AC output voltage becomes a distorted waveform whose head is crushed.

Here, assuming that the rated value of the peak value of the AC voltage output from the inverter generator is VA (<VAmax), the operating point is point P1 in FIG. 4, and the rated load current is IDA. As shown in FIG. 4, when the DC power supply voltage VD changes, the peak value of the AC output voltage is set to the rated value VA.
Assuming that a correction coefficient that needs to be multiplied by the reference duty value Do is Kv, the correction coefficient Kv is given by the following equation.

Kv = VA / VD (2) Accordingly, when the rated value of the peak value of the AC output voltage is VA, the duty value D of the PWM control is given by the following equation.

D = Sin (2πnΔt / T) × (VA / VD) (3) In the inverter generator shown in FIG. 1, the data AN0 giving the instantaneous value of the voltage between the load connection terminals 7u and 7v is supplied to the CPU 15d. When this data is smaller than the data giving the rated value, the duty value D of the PWM control is increased, and the data AN0 giving the instantaneous value of the voltage between the load connection terminals 7u and 7v is larger than the data giving the rated value. Is larger, the duty value D is corrected so as to reduce the duty value D of the PWM control, and control is performed so that the deviation between the voltage detected by the output voltage detection circuit 11 and the rated value approaches zero. I have.

The duty value D 'after such correction is given by the following equation.

D ′ = D + G × (ANS−AN0) × Kc (4) where ANS is the rated value of each instantaneous value of the AC output voltage, G
Is a gain that determines the ratio of the correction amount to the deviation between the rated values ANS and AN0. The gain G is usually set to a value of 1 or less. The coefficient Kc is a coefficient multiplied by the correction value for converting the correction value [G × (ANS-AN0)] of the instantaneous data of the voltage between the load connection terminals into the correction value of the duty value at that time. It is.

Every time the PWM cycle is detected by the PWM cycle counter, the CPU 15d reads the reference duty value D read from the ROM in accordance with the count value n of the counter.
o and the read DC power supply voltage data AN1 (= VD
) Is calculated by using the correction coefficient Kv calculated by the equation (2) and the duty value D is calculated by the equation (3) or read from a duty calculation map stored in the ROM in advance to obtain the duty value D. Find the value. The duty calculation map used here is, for example, a three-dimensional map that gives a relationship between the count value n of the counter, the output voltage data AN1 of the rectifier, and the duty value D.

In the case of performing control to make the deviation between the voltage between the load connection terminals 7u and 7v and the rated value zero, (4)
A duty value D 'corrected so as to eliminate the deviation between the output voltage data AN0 and the rated value is calculated using the equation, and the switch of the switch circuit is controlled so that the output of the switch circuit is PWM-controlled by the duty value D'. Apply a PWM signal to the device.

In the inverter power generator of FIG. 1, overload protection control is performed to protect the inverter from overload current. In the overload protection control in the conventional inverter generator, when the load current of the inverter becomes equal to or more than the overcurrent determination value for a set time, C
Turn off the port of PU15d (Enable / Disabl
The e signal is disabled), and the supply of the PWM signal to the switch element of the switch circuit 5 is stopped to cut off the overcurrent. However,
According to such a method, when the load 8 is an inductive load such as an induction motor and a large inrush current flows at the time of starting,
In some cases, the overload protection control was activated by the inrush current at the time of starting, and the load could not be started.

Therefore, in the present invention, a first overload determination value is set for the load current of the inverter, and a second overload determination value larger than the first overload determination value is set. And the load current is equal to the first overload judgment value and the second
When the overload continuation time exceeds the first set time, the supply of the drive signal to the switch circuit 5 is stopped to stop the operation of the inverter. When the load current exceeds the second overload determination value, the output voltage of the inverter (load connection terminals 7u,
Is determined to be equal to or less than the short-circuit determination value, and it is determined whether the cause of the excessive load current is a short-circuit accident occurring on the output side of the inverter. as a result,
If it is determined that a short circuit has occurred, the supply of the drive signal to the switch circuit 5 is immediately stopped to stop the operation of the inverter. If it is determined that a short circuit has not occurred, a second set time is determined according to the magnitude of the output voltage of the inverter, and when the overload duration exceeds the second set time. The supply of the drive signal to the switch circuit 5 is stopped to stop the operation of the inverter.

That is, in the overload control of the present invention,
When detecting that a load current exceeding the first overload determination value has flowed through the inverter, measurement of the overload duration is started, and the second load current is set to be larger than the first overload determination value. And whether the output voltage of the inverter is equal to or less than the short-circuit determination value is determined by determining whether the load current exceeds the second overload determination value. When the output voltage of the inverter is equal to or less than the short-circuit determination value, the operation of the inverter is immediately stopped. When the load current is equal to or greater than the first overload determination value and equal to or less than the second overload determination value, the operation of the inverter is stopped when the overload duration exceeds the first set time. Further, when the overload current exceeds the second overload determination value and the output voltage of the inverter is higher than the short-circuit determination value, it is determined that the overload current is excessive but not due to a short-circuit accident. Thus, the overload current is allowed to flow until the second set time set according to the output voltage of the inverter is exceeded, and the operation of the inverter is stopped when the overload duration exceeds the second set time. Stop. The second set time is set to be shorter as the output voltage of the inverter is lower.

FIG. 5 shows an example of an algorithm of a program to be executed by the CPU of the controller when performing the overload control as described above. In this example, the program executed by the CPU is configured to perform a series of processes by a multitasking method of repeatedly executing a large number of tasks in a predetermined order. FIG. 5 shows the configuration of one task n executed by the CPU. In this task,
First, in step 1, it is determined whether or not the overload detection circuit 14 has generated an overload signal. As a result, if the overload signal has been generated, the process proceeds to step 2 and it is determined whether or not the flag is set to 1. Since the flag has not been set to 1 immediately after the occurrence of the overload signal, the routine proceeds to step 3 where a timer provided in the microcomputer is set, and the flag is set to 1 in step 4. Next, at step 5, it is determined whether or not the detected value i of the load current exceeds the second overload determination value is2, and if the detected value of the load current exceeds the second overload determination value, Then, the process proceeds to step 6, where the output voltage of the inverter (the voltage between the load connection terminals 7u and 7v) VL
It is determined whether or not the average value Vav is equal to or less than the short-circuit determination value Vs.

The CPU 15d calculates the instantaneous value of the output voltage VL of the inverter having a waveform as shown in FIG.
As shown in (B), sampling is performed at a constant sampling cycle, the sampled voltage value is integrated over one cycle T of the voltage VL, and the integrated value is divided by the cycle T to obtain the average value of the output voltage of the inverter. Processing for calculating Vav is performed as needed. In step 6, the average value Vav of the output voltage VL of the inverter thus obtained is compared with a short-circuit determination value (average value of the output voltage when the load connection terminals are short-circuited or nearly short-circuited) Vs. I do.

As a result, when it is determined that the average value Vav of the output voltage of the inverter is equal to or less than the short-circuit determination value Vs (it is necessary to immediately stop the operation of the inverter when the load connection terminals are short-circuited or nearly short-circuited). If there is), the operation proceeds to step 7 to immediately stop the supply of the drive signal to the switch circuit 5 to stop the operation of the inverter by performing an output stop process. After stopping the operation of the inverter, the timer is reset in step 8;
Next, in step 9, the flag is reset to 0,
Return to the main routine.

When it is determined in step 5 that the detected value i of the load current is equal to or less than the second overload determination value is2,
When it is determined in step 6 that the average value Vav of the output voltage of the inverter exceeds the short-circuit determination value Vs, the set time is determined according to the detected value i of the load current and the average value Vav of the output voltage of the inverter. The process proceeds to step 10 for performing the processing for performing.

In the set time determination process of step 10, when the detected value i of the load current is equal to or less than the second overload determination value is2 (when the process proceeds from step 5 to step 10), the set time is set to the first set time. When the detected value i of the load current exceeds the second overload determination value is2 and the average value Vav of the output voltage of the inverter exceeds the short-circuit determination value Vs (when shifting from step 6 to step 10) ), The set time is the second set time. The detected value of the load current is the second
The first set time which is a set time when the load current is equal to or less than the overload determination value may be a constant value, and a time that changes according to the magnitude of the load current so as to become shorter as the load current becomes larger. It may be.

The second set time, which is the set time when the detected value of the load current exceeds the second overload judgment value, becomes shorter as the output voltage of the inverter becomes lower, and the output voltage of the inverter becomes lower. The voltage is changed according to the output voltage of the inverter so that the longer the voltage, the longer the voltage.

The setting time determination processing in step 10 may be performed every time task n is repeated.
If it is not necessary to change the previously set time when executing task n next (if the condition for determining the set time is not different from the time when task n was previously executed), step 10 is executed. Alternatively, the processing may be shifted to the next step 11 immediately without performing the processing for determining the set time.

After determining the set time in step 10, it is determined in step 11 whether the set time has elapsed from the time when the overload signal was generated. That is, step 3
It is determined whether or not the measured value (overload continuation time) of the timer set to start the timekeeping operation exceeds the set time (first set time or second set time) determined in step 10. . As a result, when it is determined that the overload continuation time exceeds the set time, the process proceeds to step 7 and the operation of the inverter is stopped. When it is determined in step 11 that the overload duration has not exceeded the set time, the process returns to the main routine.

If it is determined in step 1 that the overload signal has not been generated, the flow proceeds to step 8 to reset the timer, and in step 9 the flag is reset to 0 and the process returns to the main routine.

FIG. 7 shows an example of the overload protection operation when the load current exceeds the second overload judgment value in the present embodiment, and the horizontal axis in FIG. 7 shows the second setting. The time is shown and the vertical axis is the detected value (average value) of the output voltage of the inverter
Is shown. In FIG. 7, a polygonal line a indicates an actual detection voltage, and a staircase-like polygonal line b indicates a relationship between a set time and an inverter output voltage in an actual protection operation. In FIG. 7, a hatched area indicates a prohibited area in which the operation of the inverter is prohibited.

In the example shown in FIG. 7, the short-circuit judgment value is 10
When it is set to [V] and the average value of the detected output voltage of the inverter is in the range of zero to 10 [V], the operation of the inverter is immediately stopped. In addition, the average value of the output voltage of the inverter is 10 [V] to 30 [V].
When in the range of [V], the second set time is 1 [sec].
The operation of the inverter is stopped when 1 [sec] has elapsed after the overload state is detected.

Similarly, when the output voltage of the inverter is 30 to 5
When the voltage is in the range of 0 [V], 50 to 70 [V], and 70 to 90 [V], the second set time is 2 [sec],
When the output voltage of the inverter is set to 3 [sec] and 4 [sec] and the output voltage of the inverter is 90 [V] or more, the second set voltage is 5 [sec].
Set to [sec].

As described above, when the load current exceeds the second overcurrent judgment value and the output voltage of the inverter exceeds the short circuit judgment value, it is determined that the overload current is not caused by a short circuit accident. It is determined that the overload current flows until the overload duration reaches the second set time, and the operation of the inverter is stopped when the overload duration exceeds the second set value. When the motor is stopped, the second overload determination value and the short-circuit determination value are set to appropriate values, and the second duration is set to an appropriate value according to the output voltage of the inverter. As described above, even a load in which a large inrush current flows at the time of startup can be driven without any trouble.

In the above example, the overload detection circuit 14 shown in FIG. 1 generates an overload signal when the load current detected by the load current detector becomes equal to or greater than the first overload determination value. It constitutes an overload signal generating means.

Steps 1 to 4 of the task shown in FIG.
And steps 8 and 9 constitute an overload duration measuring means for measuring an overload duration which is an elapsed time from the time of occurrence of the overload signal.

Further, according to step 5 in FIG. 5, it is determined whether or not the load current exceeds a second overload judgment value set to a value larger than the first overload judgment value when the overload signal is generated. Is determined.

In step 6, when it is determined by the overload current determination means that the load current exceeds the second overload determination value, it is determined whether the output voltage of the inverter is equal to or less than the set short-circuit determination value. A short-circuit determining means for determining whether the output voltage of the inverter is equal to or less than the short-circuit determination value is determined by the steps 6 and 7 to provide a short-circuit inverter protecting means for immediately stopping the operation of the inverter. Be composed.

Further, according to steps 5 and 6 and steps 10 and 11 and step 7 of the task in FIG. 5, the magnitude of the load current is equal to or more than the first overload judgment value and equal to or less than the second overload judgment value. When the overload continuation time exceeds the first set time while the overload continuation time exceeds the first set time while the overload continuation time exceeds the second overload determination value. Determined by the overload current determining means,
And overload inverter protection for stopping the operation of the inverter when the overload continuation time exceeds the second set time while the short circuit determination means determines that the output voltage of the inverter is higher than the short circuit determination value. Means are configured.

As described above, when the overload current determination means, the short-circuit determination means, the short-circuit inverter protection means, and the overload inverter protection means are realized by software, the overload determination value And the short-circuit judgment value can be arbitrarily set on the software, which makes it easy to set the overload protection operation characteristics for various loads, and makes it easy to obtain an inverter generator that can handle various loads. it can.

In the above example, when the load current exceeds the second overload judgment value, the output voltage of the inverter is compared with the short circuit judgment value to determine whether the overload current is based on a short circuit accident. The load current flowing through the inverter is compared with the allowable limit value and at least one overload determination value set to a value smaller than the allowable limit value, and the load current is set to the allowable limit value. If the load current is less than the allowable limit value and any of the overload judgment values is detected, the inverter operation is stopped according to the magnitude of the overload judgment value. The operation of the inverter may be stopped when the set time elapses.

FIG. 8 shows a main configuration of the inverter power generating apparatus when overload protection control is performed by such a method.

In FIG. 8, the reference numeral 20A indicates that the load current value detected by the load current detector is compared with an allowable limit value, and the inverter is immediately stopped when it is detected that the load current exceeds the allowable limit value. An instantaneous stop command generation circuit for generating a stop command for instructing the load current detector to generate a first overcurrent determination value in which the value i of the load current detected by the load current detector is set to a value smaller than an allowable limit value When it is detected that the value of the load current detected by comparing with i1 exceeds the first overload judgment value, the timed operation is performed for a time set according to the magnitude of the overload judgment value. A first overload stop command generation circuit for generating a stop command for instructing to stop the operation of the inverter when the timed operation is completed, and 20C is a load current value detected by the load current detector. i It is detected that the value of the load current detected by comparing with the second overload determination value i2 set to a value larger than the overload determination value i1 of 1 exceeds the second overload determination value. A timed operation is performed for a time set according to the magnitude of the second overload determination value, and a stop command is issued to stop the operation of the inverter when the timed operation is completed. This is a second overload stop command generation circuit.

The instantaneous stop command generation circuit 20A includes a comparator CPa having a load current detection signal Vi input to an inverting input terminal.
And an allowable limit value signal Vim obtained by dividing the power supply voltage E obtained from a DC constant voltage power supply circuit (not shown) to the non-inverting input terminal of the comparator CPa. And a comparator C via a diode Da1 whose cathode is directed to the output terminal side of the comparator CPa.
A resistor Ra3 is connected between the output terminal of Pa and the non-inverting input terminal. The output terminal of the comparator CPa is the output terminal 20a of the instantaneous stop command generation circuit 20A.

First overload stop command generation circuit 20B
Is a first overload obtained by dividing a power supply voltage E by a series circuit of a comparator CPb1 in which a load current detection signal Vi is input to an inverting input terminal through a resistor Rao, and resistors Rb1 and Rb2. A voltage dividing circuit for inputting the judgment signal Vi1 to the non-inverting input terminal of the comparator CPb; a diode Db1 having a cathode connected to an output terminal of the comparator CPb1 via a resistor Rb3; and an output terminal of the comparator CPb1 and a diode Db1.
A resistor Rb4 connected between the anode and the comparator CP
A resistor Rb5 connected between the output terminal b1 and the positive side output terminal of the DC constant voltage power supply circuit, a timer capacitor Cb2 connected between the anode of the diode Db1 and the ground, and a voltage across the capacitor Cb2 that is not Input to the inverting input terminal,
The comparator CPb2 having the reference voltage Vr input to the inverting input terminal
It consists of In this example, the output terminal 20b of the first overload stop command generation circuit 20B is drawn out of the output terminal of the comparator CPb2.

Second overload stop command generation circuit 20C
Is a series circuit of a comparator CPc in which a load current detection signal Vi is input to an inverting input terminal through a resistor Rco, and a series circuit of resistors Rc1 and Rc2, and a second overload obtained by dividing the power supply voltage E. A voltage dividing circuit for inputting the determination signal Vi2 (> Vi1) to the non-inverting input terminal of the comparator CPc1, a diode Dc1 having a cathode connected to the output terminal of the comparator CPc1 via a resistor Rc3, and an output of the comparator CPc1. A resistor Rc4 connected between the terminal and the anode of the diode Dc1,
A resistor Rc5 connected between the output terminal of the comparator CPc1 and the positive output terminal of the DC constant voltage power supply circuit;
Timer capacitor C connected between the anode of c1 and ground
The circuit c2 and the comparator CPc2 are configured similarly to the first overload stop command generation circuit 20B. Comparator CPc2
The output terminal 20c of the second overload stop command generation circuit 22 is drawn out of the output terminal of FIG.

The output terminals 20a to 20c of the stop command generation circuits 20A to 20C are connected to the cathodes of the diodes Da2 to Dc2 constituting the OR circuit 21, respectively. Is derived.

In the instantaneous stop command generation circuit 20A,
The load current detected by the load current detection signal Vi is the first
When the voltage exceeds the allowable limit value given by the allowable limit value signal Vim, the potential of the output terminal of the comparator CPa decreases from the high level to the zero level, and the potential of the stop command output terminal 22 decreases to the zero level. The decrease in the potential of the stop command output terminal is used as a stop command signal.

In the first overload stop command generation circuit 20B, the load current detected by the load current detection signal Vi is given by the first overload determination signal Vi1.
, The output stage of the comparator CPb1 is in the open state. At this time, the capacitor Cb2 is connected to the power supply voltage E from the power supply circuit (not shown) through the resistors Rb5 and Rb4.
, The output stage of the comparator CPb2 is open.

When the load current detected by the load current detection signal Vi exceeds the first overload judgment value i1 (<im) set smaller than the allowable limit value, the load current detection signal Vi becomes the first overload judgment value Vi. Since it becomes higher than the overload determination value Vi1, the output stage of the comparator CPb1 is turned on. As a result, the electric charge stored in the capacitor Cb2 is discharged with a constant time constant through the diode Db1, the resistor Rb3, and the output stage of the comparator CPb1. After the load current exceeds the first overload judgment value, when the first set time T1 elapses, the voltage across the capacitor Cb2 becomes lower than the reference signal Vr, so that the output stage of the comparator CPb2 is turned on. As a result, the potential of the stop command output terminal 22 is changed from a high level state to a zero level state. A change in the potential of the stop command output terminal 22 at this time is a stop command.

Similarly, in the second overload inverter output stop circuit 20C, after the load current i exceeds the second overload determination value i2 and becomes Vi> Vi2, the second set time T2 is When the time has elapsed, the voltage across the capacitor Cc2 becomes lower than the reference voltage Vr. Thereby, the comparator CPc2
Is turned on, the potential of the stop command output terminal 22 is lowered, and a stop command is generated. The second set time T2 is set shorter than the first set time T1.

The stop command output terminal 22 is input to the stop command input terminal of the controller. When the stop command is output from the stop command output terminal 22,
The CPU 5 executes a predetermined program to execute the switch circuit 5
The supply of the drive signal to the inverter is stopped, and the operation of the inverter is stopped. The OR circuit 21 and the process in which the CPU stops the operation of the inverter in response to the stop command causes the inverter to operate when either the instantaneous stop command generation circuit or the overload stop command generation circuit generates a stop command. Inverter stopping means for stopping is configured.

When a stop command is generated by using a circuit as shown in FIG. 8, as shown in FIG.
After the overload is detected when the load current i is in the range of the first overload determination value i1 or more and less than the second overload determination value i2, when the first set time T1 elapses, The operation is stopped. When the load current i is in the range of not less than the second overload judgment value i2 and not more than the allowable limit value im, the second set time T2 (<
When T1) has elapsed, the operation of the inverter is stopped.

When the load current exceeds the allowable limit value im, the operation of the inverter is immediately stopped.

Therefore, for example, the first overload determination value i
1 is set to a value that gives the lower limit of the overload range for loads other than the inductive load, and the second overload determination value i2 is set to a value that gives the lower limit of the overload range for the inductive load. Can be driven without hindrance. By setting the allowable limit to an appropriate value, the inverter can be stopped instantaneously when the load connection terminals are short-circuited or nearly short-circuited, and the inverter can be protected properly. it can.

In the example shown in FIG. 8, two overload stop command generation circuits are provided.
By providing the above and setting the overload judgment value to 3 or more,
Further, fine-grained overload protection control can be performed.

The object of the present invention can be achieved by providing only one overload stop command generation circuit in addition to the instantaneous stop command generation circuit. When only one overload stop command generation circuit is provided, the overload judgment value set for the overload stop command generation circuit is set to a value that gives the lower limit of the overload range, and the instantaneous stop command generation is performed. The allowable limit value set for the circuit is set higher than the peak value of the inrush current flowing when the inductive load is started.

When a plurality of overload stop command generation circuits are provided, the time from when each of the plurality of overload stop command generation circuits detects a load current equal to or greater than the overload determination value to when a stop command is generated ( The set time is set shorter as the overload judgment value used in each stop command generation circuit is larger.

[0108]

As described above, according to the first and second aspects of the present invention, when the overload current is in the range of not less than the first overload judgment value and not more than the second overload judgment value. When the overload duration exceeds the first set time, the operation of the inverter is stopped, the overload current exceeds the second overload determination value, and the output voltage of the inverter exceeds the short-circuit determination value. In this case, when the overload continuation time exceeds a second set time set according to the output voltage of the inverter, the operation of the inverter is stopped, the overload current exceeds the second overload determination value, and When the output voltage of the inverter becomes equal to or less than the short-circuit determination value, the operation of the inverter is immediately stopped, so that the inductive load can be driven and the inverter overload protection control can be performed accurately. The advantage That.

According to the third and fourth aspects of the present invention, an allowable limit value and at least one overload judgment value are set for the load current, and the load current is equal to or larger than the overload judgment value. When the load is within the range, the operation of the inverter is stopped when the set time elapses after the overload is detected, and the operation of the inverter is stopped immediately when the load current exceeds the allowable limit. By setting the overload judgment value and the permissible limit value to appropriate values, there is an advantage that the overload protection control of the inverter can be performed accurately while permitting the driving of the inductive load.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of an inverter power generation device according to the present invention.

FIG. 2 is a time chart showing a drive signal given to a switch circuit of an inverter and an on / off timing of a switch element in the inverter power generator of FIG.

FIG. 3 is an explanatory diagram showing a waveform of an AC voltage obtained between load connection terminals and an internal interrupt timing in PWM control in the inverter power generator of FIG. 1;

FIG. 4 is a diagram illustrating an example of output characteristics of a DC power supply unit of the inverter power generation device of FIG. 1;

FIG. 5 is a flowchart illustrating a main part of an algorithm of a program executed by a controller of the inverter power generation device of FIG. 1;

FIGS. 6A and 6B are waveform diagrams showing an AC voltage waveform obtained from an inverter power generator and sampling timing when an average value of the AC voltage is obtained.

FIG. 7 is a diagram for describing overload protection control when the algorithm shown in FIG. 5 is followed.

FIG. 8 is a circuit diagram showing a configuration example of a stop command generation circuit portion when an inverter stop command is generated at the time of overload using a hardware circuit in the present invention.

FIG. 9 is a diagram illustrating an overload protection operation when the circuit of FIG. 8 is used.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Inverter generator, 2 ... Alternator, 3 ... Internal combustion engine, 4A ... Rectifier, 4 ... DC power supply unit, 5 ... Switch circuit, 6 ... Filter circuit, 7u, 7v ... Load connection terminal, 8
... Load, 10 ... Power supply voltage detection circuit, 11 ... Output voltage detection circuit, 12 ... Load current detector, 13 ... Amplification circuit, 14 ...
Overload detection circuit, 15 ... controller.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5G004 AB02 BA03 BA04 DC01 DC14 EA01 5G053 AA01 AA02 AA05 BA01 BA04 CA02 EA03 EB01 EC03 FA04 5H590 AA30 AB03 CA07 CC02 CC24 CD01 CD03 DD06 EA05 FA08 FB02 GA04 HA04 HB03

Claims (4)

[Claims] 1. An AC generator driven by an internal combustion engine, a rectifier for rectifying an output of the AC generator, and an inverter for converting an output voltage of the rectifier into an AC voltage having a constant frequency and supplying the AC voltage to a load. An overload control method for an inverter power generating device comprising: when detecting that a load current exceeding a first overload determination value has flowed through the inverter, starting measurement of an overload duration. It is determined whether or not the load current exceeds a second overload determination value set to be larger than the first overload determination value, and whether or not the output voltage of the inverter is equal to or less than a short-circuit determination value. And when the load current exceeds the second overload determination value and the output voltage of the inverter is equal to or less than the short-circuit determination value, the operation of the inverter is stopped immediately. Is not less than the first overload judgment value and not more than the second overload judgment value, the operation of the inverter is stopped when the overload continuation time exceeds a first set time; When the overload current exceeds the second overload determination value and the output voltage of the inverter is higher than the short circuit determination value, the second setting in which the overload duration is set according to the output voltage of the inverter When the time exceeds a time, the second set time is set to be shorter as the output voltage of the inverter is lower, Control method. 2. An AC generator driven by an internal combustion engine, a rectifier for rectifying an output of the AC generator, and an inverter for converting an output voltage of the rectifier into an AC voltage having a constant frequency and supplying the AC voltage to a load. A load current detector for detecting a load current flowing from the inverter to a load, and a load current detected by the load current detector being equal to or greater than a first overload determination value. An overload signal generating unit that generates an overload signal; an overload duration measuring unit that measures an overload duration that is an elapsed time from a time when the overload signal is generated; and when the overload signal is generated. An overload current determination unit configured to determine whether the load current exceeds a second overload determination value set to a value greater than the first overload determination value; The load current is the by the constant means second
Short-circuit determination means for determining whether or not the output voltage of the inverter is equal to or less than a set short-circuit determination value when it is determined that the inverter has exceeded the overload determination value of the inverter; A short-circuit inverter protection means for immediately stopping the operation of the inverter when it is determined that the output voltage is equal to or less than the short-circuit determination value; and the magnitude of the load current is determined by the overload current determination means. When the overload continuation time exceeds a first set time in a state where it is determined that the load is equal to or more than the load determination value and is equal to or less than the second overload determination value, and that the load is determined by the overload current determination unit. It is determined that the magnitude of the current exceeds the second overload determination value, and the output voltage of the inverter is determined by the short-circuit determination means to be higher than the short-circuit determination value. An overload inverter protection means for stopping the operation of the inverter when the overload continuation time exceeds a second set time in the state, wherein the output voltage of the inverter is the second set time. The inverter power generator is set to be shorter when the power is lower. 3. An AC generator driven by an internal combustion engine, a rectifier for rectifying an output of the AC generator, and an inverter for converting an output voltage of the rectifier into an AC voltage having a constant frequency and supplying the AC voltage to a load. In the control method at the time of overload of the inverter power generating device, the value of the load current flowing through the inverter is set to an allowable limit value and at least one of a value smaller than the allowable limit value.
Comparing the two overload determination values, immediately stop the operation of the inverter when the load current exceeds the allowable limit value, the load current is less than the allowable limit value, and any of the overload determination values Overrunning the inverter when the time set according to the magnitude of the overload determination value elapses, the operation of the inverter is stopped. . 4. An AC generator driven by an internal combustion engine, a rectifier for rectifying the output of the AC generator, and an inverter for converting an output voltage of the rectifier into an AC voltage having a constant frequency and supplying the AC voltage to a load. A load current detector for detecting a load current flowing through the inverter, and comparing the value of the load current detected by the load current detector with an allowable limit value so that the load current is equal to an allowable limit. An instantaneous stop command generating circuit that generates a stop command for instructing to stop the inverter immediately when it is detected that the value has exceeded the value, the load current value detected by the load current detector is set to the allowable limit value. When it is detected that the value of the load current detected in comparison with the overload determination value set to a value smaller than the overload determination value exceeds the overload determination value, Perform a timed operation for a set time set according to the size of
At least one overload stop command generation circuit that generates a stop command for commanding to stop the operation of the inverter when the timed operation is completed; and the instantaneous stop command generation circuit or the overload stop command generation circuit. And an inverter stopping means for stopping the operation of the inverter when any one of the above generates a stop command.